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</head>

<body>




<h1 class="title toc-ignore">Grouped data</h1>



<p>dplyr verbs are particularly powerful when you apply them to grouped
data frames (<code>grouped_df</code> objects). This vignette shows
you:</p>
<ul>
<li><p>How to group, inspect, and ungroup with <code>group_by()</code>
and friends.</p></li>
<li><p>How individual dplyr verbs changes their behaviour when applied
to grouped data frame.</p></li>
<li><p>How to access data about the “current” group from within a
verb.</p></li>
</ul>
<p>We’ll start by loading dplyr:</p>
<div class="sourceCode" id="cb1"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb1-1"><a href="#cb1-1" aria-hidden="true" tabindex="-1"></a><span class="fu">library</span>(dplyr)</span></code></pre></div>
<div id="group_by" class="section level2">
<h2><code>group_by()</code></h2>
<p>The most important grouping verb is <code>group_by()</code>: it takes
a data frame and one or more variables to group by:</p>
<div class="sourceCode" id="cb2"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb2-1"><a href="#cb2-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="ot">&lt;-</span> starwars <span class="sc">%&gt;%</span> <span class="fu">group_by</span>(species)</span>
<span id="cb2-2"><a href="#cb2-2" aria-hidden="true" tabindex="-1"></a>by_sex_gender <span class="ot">&lt;-</span> starwars <span class="sc">%&gt;%</span> <span class="fu">group_by</span>(sex, gender)</span></code></pre></div>
<p>You can see the grouping when you print the data:</p>
<div class="sourceCode" id="cb3"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb3-1"><a href="#cb3-1" aria-hidden="true" tabindex="-1"></a>by_species</span>
<span id="cb3-2"><a href="#cb3-2" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 87 × 14</span></span>
<span id="cb3-3"><a href="#cb3-3" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # Groups:   species [38]</span></span>
<span id="cb3-4"><a href="#cb3-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   name      height  mass hair_color skin_color eye_color birth_year sex   gender</span></span>
<span id="cb3-5"><a href="#cb3-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;      &lt;int&gt; &lt;dbl&gt; &lt;chr&gt;      &lt;chr&gt;      &lt;chr&gt;          &lt;dbl&gt; &lt;chr&gt; &lt;chr&gt; </span></span>
<span id="cb3-6"><a href="#cb3-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Luke Sky…    172    77 blond      fair       blue            19   male  mascu…</span></span>
<span id="cb3-7"><a href="#cb3-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 C-3PO        167    75 &lt;NA&gt;       gold       yellow         112   none  mascu…</span></span>
<span id="cb3-8"><a href="#cb3-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 R2-D2         96    32 &lt;NA&gt;       white, bl… red             33   none  mascu…</span></span>
<span id="cb3-9"><a href="#cb3-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Darth Va…    202   136 none       white      yellow          41.9 male  mascu…</span></span>
<span id="cb3-10"><a href="#cb3-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 83 more rows</span></span>
<span id="cb3-11"><a href="#cb3-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 5 more variables: homeworld &lt;chr&gt;, species &lt;chr&gt;, films &lt;list&gt;,</span></span>
<span id="cb3-12"><a href="#cb3-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; #   vehicles &lt;list&gt;, starships &lt;list&gt;</span></span>
<span id="cb3-13"><a href="#cb3-13" aria-hidden="true" tabindex="-1"></a>by_sex_gender</span>
<span id="cb3-14"><a href="#cb3-14" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 87 × 14</span></span>
<span id="cb3-15"><a href="#cb3-15" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # Groups:   sex, gender [6]</span></span>
<span id="cb3-16"><a href="#cb3-16" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   name      height  mass hair_color skin_color eye_color birth_year sex   gender</span></span>
<span id="cb3-17"><a href="#cb3-17" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;      &lt;int&gt; &lt;dbl&gt; &lt;chr&gt;      &lt;chr&gt;      &lt;chr&gt;          &lt;dbl&gt; &lt;chr&gt; &lt;chr&gt; </span></span>
<span id="cb3-18"><a href="#cb3-18" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Luke Sky…    172    77 blond      fair       blue            19   male  mascu…</span></span>
<span id="cb3-19"><a href="#cb3-19" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 C-3PO        167    75 &lt;NA&gt;       gold       yellow         112   none  mascu…</span></span>
<span id="cb3-20"><a href="#cb3-20" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 R2-D2         96    32 &lt;NA&gt;       white, bl… red             33   none  mascu…</span></span>
<span id="cb3-21"><a href="#cb3-21" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Darth Va…    202   136 none       white      yellow          41.9 male  mascu…</span></span>
<span id="cb3-22"><a href="#cb3-22" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 83 more rows</span></span>
<span id="cb3-23"><a href="#cb3-23" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 5 more variables: homeworld &lt;chr&gt;, species &lt;chr&gt;, films &lt;list&gt;,</span></span>
<span id="cb3-24"><a href="#cb3-24" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; #   vehicles &lt;list&gt;, starships &lt;list&gt;</span></span></code></pre></div>
<p>Or use <code>tally()</code> to count the number of rows in each
group. The <code>sort</code> argument is useful if you want to see the
largest groups up front.</p>
<div class="sourceCode" id="cb4"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb4-1"><a href="#cb4-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span> <span class="fu">tally</span>()</span>
<span id="cb4-2"><a href="#cb4-2" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 38 × 2</span></span>
<span id="cb4-3"><a href="#cb4-3" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   species      n</span></span>
<span id="cb4-4"><a href="#cb4-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;    &lt;int&gt;</span></span>
<span id="cb4-5"><a href="#cb4-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Aleena       1</span></span>
<span id="cb4-6"><a href="#cb4-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 Besalisk     1</span></span>
<span id="cb4-7"><a href="#cb4-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 Cerean       1</span></span>
<span id="cb4-8"><a href="#cb4-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Chagrian     1</span></span>
<span id="cb4-9"><a href="#cb4-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 34 more rows</span></span>
<span id="cb4-10"><a href="#cb4-10" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb4-11"><a href="#cb4-11" aria-hidden="true" tabindex="-1"></a>by_sex_gender <span class="sc">%&gt;%</span> <span class="fu">tally</span>(<span class="at">sort =</span> <span class="cn">TRUE</span>)</span>
<span id="cb4-12"><a href="#cb4-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 6 × 3</span></span>
<span id="cb4-13"><a href="#cb4-13" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # Groups:   sex [5]</span></span>
<span id="cb4-14"><a href="#cb4-14" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   sex    gender        n</span></span>
<span id="cb4-15"><a href="#cb4-15" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;  &lt;chr&gt;     &lt;int&gt;</span></span>
<span id="cb4-16"><a href="#cb4-16" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 male   masculine    60</span></span>
<span id="cb4-17"><a href="#cb4-17" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 female feminine     16</span></span>
<span id="cb4-18"><a href="#cb4-18" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 none   masculine     5</span></span>
<span id="cb4-19"><a href="#cb4-19" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 &lt;NA&gt;   &lt;NA&gt;          4</span></span>
<span id="cb4-20"><a href="#cb4-20" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 2 more rows</span></span></code></pre></div>
<p>As well as grouping by existing variables, you can group by any
function of existing variables. This is equivalent to performing a
<code>mutate()</code> <strong>before</strong> the
<code>group_by()</code>:</p>
<div class="sourceCode" id="cb5"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb5-1"><a href="#cb5-1" aria-hidden="true" tabindex="-1"></a>bmi_breaks <span class="ot">&lt;-</span> <span class="fu">c</span>(<span class="dv">0</span>, <span class="fl">18.5</span>, <span class="dv">25</span>, <span class="dv">30</span>, <span class="cn">Inf</span>)</span>
<span id="cb5-2"><a href="#cb5-2" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb5-3"><a href="#cb5-3" aria-hidden="true" tabindex="-1"></a>starwars <span class="sc">%&gt;%</span></span>
<span id="cb5-4"><a href="#cb5-4" aria-hidden="true" tabindex="-1"></a>  <span class="fu">group_by</span>(<span class="at">bmi_cat =</span> <span class="fu">cut</span>(mass<span class="sc">/</span>(height<span class="sc">/</span><span class="dv">100</span>)<span class="sc">^</span><span class="dv">2</span>, <span class="at">breaks=</span>bmi_breaks)) <span class="sc">%&gt;%</span></span>
<span id="cb5-5"><a href="#cb5-5" aria-hidden="true" tabindex="-1"></a>  <span class="fu">tally</span>()</span>
<span id="cb5-6"><a href="#cb5-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 5 × 2</span></span>
<span id="cb5-7"><a href="#cb5-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   bmi_cat       n</span></span>
<span id="cb5-8"><a href="#cb5-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;fct&gt;     &lt;int&gt;</span></span>
<span id="cb5-9"><a href="#cb5-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 (0,18.5]     10</span></span>
<span id="cb5-10"><a href="#cb5-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 (18.5,25]    24</span></span>
<span id="cb5-11"><a href="#cb5-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 (25,30]      13</span></span>
<span id="cb5-12"><a href="#cb5-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 (30,Inf]     12</span></span>
<span id="cb5-13"><a href="#cb5-13" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 1 more row</span></span></code></pre></div>
</div>
<div id="group-metadata" class="section level2">
<h2>Group metadata</h2>
<p>You can see underlying group data with <code>group_keys()</code>. It
has one row for each group and one column for each grouping
variable:</p>
<div class="sourceCode" id="cb6"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb6-1"><a href="#cb6-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span> <span class="fu">group_keys</span>()</span>
<span id="cb6-2"><a href="#cb6-2" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 38 × 1</span></span>
<span id="cb6-3"><a href="#cb6-3" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   species </span></span>
<span id="cb6-4"><a href="#cb6-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;   </span></span>
<span id="cb6-5"><a href="#cb6-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Aleena  </span></span>
<span id="cb6-6"><a href="#cb6-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 Besalisk</span></span>
<span id="cb6-7"><a href="#cb6-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 Cerean  </span></span>
<span id="cb6-8"><a href="#cb6-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Chagrian</span></span>
<span id="cb6-9"><a href="#cb6-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 34 more rows</span></span>
<span id="cb6-10"><a href="#cb6-10" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb6-11"><a href="#cb6-11" aria-hidden="true" tabindex="-1"></a>by_sex_gender <span class="sc">%&gt;%</span> <span class="fu">group_keys</span>()</span>
<span id="cb6-12"><a href="#cb6-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 6 × 2</span></span>
<span id="cb6-13"><a href="#cb6-13" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   sex            gender   </span></span>
<span id="cb6-14"><a href="#cb6-14" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;          &lt;chr&gt;    </span></span>
<span id="cb6-15"><a href="#cb6-15" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 female         feminine </span></span>
<span id="cb6-16"><a href="#cb6-16" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 hermaphroditic masculine</span></span>
<span id="cb6-17"><a href="#cb6-17" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 male           masculine</span></span>
<span id="cb6-18"><a href="#cb6-18" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 none           feminine </span></span>
<span id="cb6-19"><a href="#cb6-19" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 2 more rows</span></span></code></pre></div>
<p>You can see which group each row belongs to with
<code>group_indices()</code>:</p>
<div class="sourceCode" id="cb7"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb7-1"><a href="#cb7-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span> <span class="fu">group_indices</span>()</span>
<span id="cb7-2"><a href="#cb7-2" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;  [1] 11  6  6 11 11 11 11  6 11 11 11 11 34 11 24 12 11 11 36 11 11  6 31 11 11</span></span>
<span id="cb7-3"><a href="#cb7-3" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [26] 18 11 11  8 26 11 21 11 10 10 10 38 30  7 38 11 37 32 32 33 35 29 11  3 20</span></span>
<span id="cb7-4"><a href="#cb7-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [51] 37 27 13 23 16  4 11 11 11  9 17 17 11 11 11 11  5  2 15 15 11  1  6 25 19</span></span>
<span id="cb7-5"><a href="#cb7-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [76] 28 14 34 11 38 22 11 11 11  6 38 11</span></span></code></pre></div>
<p>And which rows each group contains with
<code>group_rows()</code>:</p>
<div class="sourceCode" id="cb8"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb8-1"><a href="#cb8-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span> <span class="fu">group_rows</span>() <span class="sc">%&gt;%</span> <span class="fu">head</span>()</span>
<span id="cb8-2"><a href="#cb8-2" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; &lt;list_of&lt;integer&gt;[6]&gt;</span></span>
<span id="cb8-3"><a href="#cb8-3" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [[1]]</span></span>
<span id="cb8-4"><a href="#cb8-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [1] 72</span></span>
<span id="cb8-5"><a href="#cb8-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; </span></span>
<span id="cb8-6"><a href="#cb8-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [[2]]</span></span>
<span id="cb8-7"><a href="#cb8-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [1] 68</span></span>
<span id="cb8-8"><a href="#cb8-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; </span></span>
<span id="cb8-9"><a href="#cb8-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [[3]]</span></span>
<span id="cb8-10"><a href="#cb8-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [1] 49</span></span>
<span id="cb8-11"><a href="#cb8-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; </span></span>
<span id="cb8-12"><a href="#cb8-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [[4]]</span></span>
<span id="cb8-13"><a href="#cb8-13" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [1] 56</span></span>
<span id="cb8-14"><a href="#cb8-14" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; </span></span>
<span id="cb8-15"><a href="#cb8-15" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [[5]]</span></span>
<span id="cb8-16"><a href="#cb8-16" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [1] 67</span></span>
<span id="cb8-17"><a href="#cb8-17" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; </span></span>
<span id="cb8-18"><a href="#cb8-18" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [[6]]</span></span>
<span id="cb8-19"><a href="#cb8-19" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [1]  2  3  8 22 73 85</span></span></code></pre></div>
<p>Use <code>group_vars()</code> if you just want the names of the
grouping variables:</p>
<div class="sourceCode" id="cb9"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb9-1"><a href="#cb9-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span> <span class="fu">group_vars</span>()</span>
<span id="cb9-2"><a href="#cb9-2" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [1] &quot;species&quot;</span></span>
<span id="cb9-3"><a href="#cb9-3" aria-hidden="true" tabindex="-1"></a>by_sex_gender <span class="sc">%&gt;%</span> <span class="fu">group_vars</span>()</span>
<span id="cb9-4"><a href="#cb9-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [1] &quot;sex&quot;    &quot;gender&quot;</span></span></code></pre></div>
<div id="changing-and-adding-to-grouping-variables" class="section level3">
<h3>Changing and adding to grouping variables</h3>
<p>If you apply <code>group_by()</code> to an already grouped dataset,
will overwrite the existing grouping variables. For example, the
following code groups by <code>homeworld</code> instead of
<code>species</code>:</p>
<div class="sourceCode" id="cb10"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb10-1"><a href="#cb10-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span></span>
<span id="cb10-2"><a href="#cb10-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">group_by</span>(homeworld) <span class="sc">%&gt;%</span></span>
<span id="cb10-3"><a href="#cb10-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">tally</span>()</span>
<span id="cb10-4"><a href="#cb10-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 49 × 2</span></span>
<span id="cb10-5"><a href="#cb10-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   homeworld       n</span></span>
<span id="cb10-6"><a href="#cb10-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;       &lt;int&gt;</span></span>
<span id="cb10-7"><a href="#cb10-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Alderaan        3</span></span>
<span id="cb10-8"><a href="#cb10-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 Aleen Minor     1</span></span>
<span id="cb10-9"><a href="#cb10-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 Bespin          1</span></span>
<span id="cb10-10"><a href="#cb10-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Bestine IV      1</span></span>
<span id="cb10-11"><a href="#cb10-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 45 more rows</span></span></code></pre></div>
<p>To <strong>augment</strong> the grouping, using
<code>.add = TRUE</code><a href="#fn1" class="footnote-ref" id="fnref1"><sup>1</sup></a>. For example, the following code groups by
species and homeworld:</p>
<div class="sourceCode" id="cb11"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb11-1"><a href="#cb11-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span></span>
<span id="cb11-2"><a href="#cb11-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">group_by</span>(homeworld, <span class="at">.add =</span> <span class="cn">TRUE</span>) <span class="sc">%&gt;%</span></span>
<span id="cb11-3"><a href="#cb11-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">tally</span>()</span>
<span id="cb11-4"><a href="#cb11-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 58 × 3</span></span>
<span id="cb11-5"><a href="#cb11-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # Groups:   species [38]</span></span>
<span id="cb11-6"><a href="#cb11-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   species  homeworld       n</span></span>
<span id="cb11-7"><a href="#cb11-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;    &lt;chr&gt;       &lt;int&gt;</span></span>
<span id="cb11-8"><a href="#cb11-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Aleena   Aleen Minor     1</span></span>
<span id="cb11-9"><a href="#cb11-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 Besalisk Ojom            1</span></span>
<span id="cb11-10"><a href="#cb11-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 Cerean   Cerea           1</span></span>
<span id="cb11-11"><a href="#cb11-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Chagrian Champala        1</span></span>
<span id="cb11-12"><a href="#cb11-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 54 more rows</span></span></code></pre></div>
</div>
<div id="removing-grouping-variables" class="section level3">
<h3>Removing grouping variables</h3>
<p>To remove all grouping variables, use <code>ungroup()</code>:</p>
<div class="sourceCode" id="cb12"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb12-1"><a href="#cb12-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span></span>
<span id="cb12-2"><a href="#cb12-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">ungroup</span>() <span class="sc">%&gt;%</span></span>
<span id="cb12-3"><a href="#cb12-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">tally</span>()</span>
<span id="cb12-4"><a href="#cb12-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 1 × 1</span></span>
<span id="cb12-5"><a href="#cb12-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;       n</span></span>
<span id="cb12-6"><a href="#cb12-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;int&gt;</span></span>
<span id="cb12-7"><a href="#cb12-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1    87</span></span></code></pre></div>
<p>You can also choose to selectively ungroup by listing the variables
you want to remove:</p>
<div class="sourceCode" id="cb13"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb13-1"><a href="#cb13-1" aria-hidden="true" tabindex="-1"></a>by_sex_gender <span class="sc">%&gt;%</span> </span>
<span id="cb13-2"><a href="#cb13-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">ungroup</span>(sex) <span class="sc">%&gt;%</span> </span>
<span id="cb13-3"><a href="#cb13-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">tally</span>()</span>
<span id="cb13-4"><a href="#cb13-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 3 × 2</span></span>
<span id="cb13-5"><a href="#cb13-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   gender        n</span></span>
<span id="cb13-6"><a href="#cb13-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;     &lt;int&gt;</span></span>
<span id="cb13-7"><a href="#cb13-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 feminine     17</span></span>
<span id="cb13-8"><a href="#cb13-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 masculine    66</span></span>
<span id="cb13-9"><a href="#cb13-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 &lt;NA&gt;          4</span></span></code></pre></div>
</div>
</div>
<div id="verbs" class="section level2">
<h2>Verbs</h2>
<p>The following sections describe how grouping affects the main dplyr
verbs.</p>
<div id="summarise" class="section level3">
<h3><code>summarise()</code></h3>
<p><code>summarise()</code> computes a summary for each group. This
means that it starts from <code>group_keys()</code>, adding summary
variables to the right hand side:</p>
<div class="sourceCode" id="cb14"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb14-1"><a href="#cb14-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span></span>
<span id="cb14-2"><a href="#cb14-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">summarise</span>(</span>
<span id="cb14-3"><a href="#cb14-3" aria-hidden="true" tabindex="-1"></a>    <span class="at">n =</span> <span class="fu">n</span>(),</span>
<span id="cb14-4"><a href="#cb14-4" aria-hidden="true" tabindex="-1"></a>    <span class="at">height =</span> <span class="fu">mean</span>(height, <span class="at">na.rm =</span> <span class="cn">TRUE</span>)</span>
<span id="cb14-5"><a href="#cb14-5" aria-hidden="true" tabindex="-1"></a>  )</span>
<span id="cb14-6"><a href="#cb14-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 38 × 3</span></span>
<span id="cb14-7"><a href="#cb14-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   species      n height</span></span>
<span id="cb14-8"><a href="#cb14-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;    &lt;int&gt;  &lt;dbl&gt;</span></span>
<span id="cb14-9"><a href="#cb14-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Aleena       1     79</span></span>
<span id="cb14-10"><a href="#cb14-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 Besalisk     1    198</span></span>
<span id="cb14-11"><a href="#cb14-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 Cerean       1    198</span></span>
<span id="cb14-12"><a href="#cb14-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Chagrian     1    196</span></span>
<span id="cb14-13"><a href="#cb14-13" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 34 more rows</span></span></code></pre></div>
<p>The <code>.groups=</code> argument controls the grouping structure of
the output. The historical behaviour of removing the right hand side
grouping variable corresponds to <code>.groups = &quot;drop_last&quot;</code>
without a message or <code>.groups = NULL</code> with a message (the
default).</p>
<div class="sourceCode" id="cb15"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb15-1"><a href="#cb15-1" aria-hidden="true" tabindex="-1"></a>by_sex_gender <span class="sc">%&gt;%</span> </span>
<span id="cb15-2"><a href="#cb15-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">summarise</span>(<span class="at">n =</span> <span class="fu">n</span>()) <span class="sc">%&gt;%</span> </span>
<span id="cb15-3"><a href="#cb15-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">group_vars</span>()</span>
<span id="cb15-4"><a href="#cb15-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; `summarise()` has grouped output by &#39;sex&#39;. You can override using the `.groups`</span></span>
<span id="cb15-5"><a href="#cb15-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; argument.</span></span>
<span id="cb15-6"><a href="#cb15-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [1] &quot;sex&quot;</span></span>
<span id="cb15-7"><a href="#cb15-7" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb15-8"><a href="#cb15-8" aria-hidden="true" tabindex="-1"></a>by_sex_gender <span class="sc">%&gt;%</span> </span>
<span id="cb15-9"><a href="#cb15-9" aria-hidden="true" tabindex="-1"></a>  <span class="fu">summarise</span>(<span class="at">n =</span> <span class="fu">n</span>(), <span class="at">.groups =</span> <span class="st">&quot;drop_last&quot;</span>) <span class="sc">%&gt;%</span> </span>
<span id="cb15-10"><a href="#cb15-10" aria-hidden="true" tabindex="-1"></a>  <span class="fu">group_vars</span>()</span>
<span id="cb15-11"><a href="#cb15-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [1] &quot;sex&quot;</span></span></code></pre></div>
<p>Since version 1.0.0 the groups may also be kept
(<code>.groups = &quot;keep&quot;</code>) or dropped
(<code>.groups = &quot;drop&quot;</code>).</p>
<div class="sourceCode" id="cb16"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb16-1"><a href="#cb16-1" aria-hidden="true" tabindex="-1"></a>by_sex_gender <span class="sc">%&gt;%</span> </span>
<span id="cb16-2"><a href="#cb16-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">summarise</span>(<span class="at">n =</span> <span class="fu">n</span>(), <span class="at">.groups =</span> <span class="st">&quot;keep&quot;</span>) <span class="sc">%&gt;%</span> </span>
<span id="cb16-3"><a href="#cb16-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">group_vars</span>()</span>
<span id="cb16-4"><a href="#cb16-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; [1] &quot;sex&quot;    &quot;gender&quot;</span></span>
<span id="cb16-5"><a href="#cb16-5" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb16-6"><a href="#cb16-6" aria-hidden="true" tabindex="-1"></a>by_sex_gender <span class="sc">%&gt;%</span> </span>
<span id="cb16-7"><a href="#cb16-7" aria-hidden="true" tabindex="-1"></a>  <span class="fu">summarise</span>(<span class="at">n =</span> <span class="fu">n</span>(), <span class="at">.groups =</span> <span class="st">&quot;drop&quot;</span>) <span class="sc">%&gt;%</span> </span>
<span id="cb16-8"><a href="#cb16-8" aria-hidden="true" tabindex="-1"></a>  <span class="fu">group_vars</span>()</span>
<span id="cb16-9"><a href="#cb16-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; character(0)</span></span></code></pre></div>
<p>When the output no longer have grouping variables, it becomes
ungrouped (i.e. a regular tibble).</p>
</div>
<div id="select-rename-and-relocate" class="section level3">
<h3><code>select()</code>, <code>rename()</code>, and
<code>relocate()</code></h3>
<p><code>rename()</code> and <code>relocate()</code> behave identically
with grouped and ungrouped data because they only affect the name or
position of existing columns. Grouped <code>select()</code> is almost
identical to ungrouped select, except that it always includes the
grouping variables:</p>
<div class="sourceCode" id="cb17"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb17-1"><a href="#cb17-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span> <span class="fu">select</span>(mass)</span>
<span id="cb17-2"><a href="#cb17-2" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; Adding missing grouping variables: `species`</span></span>
<span id="cb17-3"><a href="#cb17-3" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 87 × 2</span></span>
<span id="cb17-4"><a href="#cb17-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # Groups:   species [38]</span></span>
<span id="cb17-5"><a href="#cb17-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   species  mass</span></span>
<span id="cb17-6"><a href="#cb17-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;   &lt;dbl&gt;</span></span>
<span id="cb17-7"><a href="#cb17-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Human      77</span></span>
<span id="cb17-8"><a href="#cb17-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 Droid      75</span></span>
<span id="cb17-9"><a href="#cb17-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 Droid      32</span></span>
<span id="cb17-10"><a href="#cb17-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Human     136</span></span>
<span id="cb17-11"><a href="#cb17-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 83 more rows</span></span></code></pre></div>
<p>If you don’t want the grouping variables, you’ll have to first
<code>ungroup()</code>. (This design is possibly a mistake, but we’re
stuck with it for now.)</p>
</div>
<div id="arrange" class="section level3">
<h3><code>arrange()</code></h3>
<p>Grouped <code>arrange()</code> is the same as ungrouped
<code>arrange()</code>, unless you set <code>.by_group = TRUE</code>, in
which case it will order first by the grouping variables.</p>
<div class="sourceCode" id="cb18"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb18-1"><a href="#cb18-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span></span>
<span id="cb18-2"><a href="#cb18-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">arrange</span>(<span class="fu">desc</span>(mass)) <span class="sc">%&gt;%</span></span>
<span id="cb18-3"><a href="#cb18-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">relocate</span>(species, mass)</span>
<span id="cb18-4"><a href="#cb18-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 87 × 14</span></span>
<span id="cb18-5"><a href="#cb18-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # Groups:   species [38]</span></span>
<span id="cb18-6"><a href="#cb18-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   species  mass name     height hair_color skin_color eye_color birth_year sex  </span></span>
<span id="cb18-7"><a href="#cb18-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;   &lt;dbl&gt; &lt;chr&gt;     &lt;int&gt; &lt;chr&gt;      &lt;chr&gt;      &lt;chr&gt;          &lt;dbl&gt; &lt;chr&gt;</span></span>
<span id="cb18-8"><a href="#cb18-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Hutt     1358 Jabba D…    175 &lt;NA&gt;       green-tan… orange         600   herm…</span></span>
<span id="cb18-9"><a href="#cb18-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 Kaleesh   159 Grievous    216 none       brown, wh… green, y…       NA   male </span></span>
<span id="cb18-10"><a href="#cb18-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 Droid     140 IG-88       200 none       metal      red             15   none </span></span>
<span id="cb18-11"><a href="#cb18-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Human     136 Darth V…    202 none       white      yellow          41.9 male </span></span>
<span id="cb18-12"><a href="#cb18-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 83 more rows</span></span>
<span id="cb18-13"><a href="#cb18-13" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 5 more variables: gender &lt;chr&gt;, homeworld &lt;chr&gt;, films &lt;list&gt;,</span></span>
<span id="cb18-14"><a href="#cb18-14" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; #   vehicles &lt;list&gt;, starships &lt;list&gt;</span></span>
<span id="cb18-15"><a href="#cb18-15" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb18-16"><a href="#cb18-16" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span></span>
<span id="cb18-17"><a href="#cb18-17" aria-hidden="true" tabindex="-1"></a>  <span class="fu">arrange</span>(<span class="fu">desc</span>(mass), <span class="at">.by_group =</span> <span class="cn">TRUE</span>) <span class="sc">%&gt;%</span></span>
<span id="cb18-18"><a href="#cb18-18" aria-hidden="true" tabindex="-1"></a>  <span class="fu">relocate</span>(species, mass)</span>
<span id="cb18-19"><a href="#cb18-19" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 87 × 14</span></span>
<span id="cb18-20"><a href="#cb18-20" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # Groups:   species [38]</span></span>
<span id="cb18-21"><a href="#cb18-21" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   species   mass name    height hair_color skin_color eye_color birth_year sex  </span></span>
<span id="cb18-22"><a href="#cb18-22" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;    &lt;dbl&gt; &lt;chr&gt;    &lt;int&gt; &lt;chr&gt;      &lt;chr&gt;      &lt;chr&gt;          &lt;dbl&gt; &lt;chr&gt;</span></span>
<span id="cb18-23"><a href="#cb18-23" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Aleena      15 Ratts …     79 none       grey, blue unknown           NA male </span></span>
<span id="cb18-24"><a href="#cb18-24" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 Besalisk   102 Dexter…    198 none       brown      yellow            NA male </span></span>
<span id="cb18-25"><a href="#cb18-25" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 Cerean      82 Ki-Adi…    198 white      pale       yellow            92 male </span></span>
<span id="cb18-26"><a href="#cb18-26" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Chagrian    NA Mas Am…    196 none       blue       blue              NA male </span></span>
<span id="cb18-27"><a href="#cb18-27" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 83 more rows</span></span>
<span id="cb18-28"><a href="#cb18-28" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 5 more variables: gender &lt;chr&gt;, homeworld &lt;chr&gt;, films &lt;list&gt;,</span></span>
<span id="cb18-29"><a href="#cb18-29" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; #   vehicles &lt;list&gt;, starships &lt;list&gt;</span></span></code></pre></div>
<p>Note that second example is sorted by <code>species</code> (from the
<code>group_by()</code> statement) and then by <code>mass</code> (within
species).</p>
</div>
<div id="mutate" class="section level3">
<h3><code>mutate()</code></h3>
<p>In simple cases with vectorised functions, grouped and ungrouped
<code>mutate()</code> give the same results. They differ when used with
summary functions:</p>
<div class="sourceCode" id="cb19"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb19-1"><a href="#cb19-1" aria-hidden="true" tabindex="-1"></a><span class="co"># Subtract off global mean</span></span>
<span id="cb19-2"><a href="#cb19-2" aria-hidden="true" tabindex="-1"></a>starwars <span class="sc">%&gt;%</span> </span>
<span id="cb19-3"><a href="#cb19-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">select</span>(name, homeworld, mass) <span class="sc">%&gt;%</span> </span>
<span id="cb19-4"><a href="#cb19-4" aria-hidden="true" tabindex="-1"></a>  <span class="fu">mutate</span>(<span class="at">standard_mass =</span> mass <span class="sc">-</span> <span class="fu">mean</span>(mass, <span class="at">na.rm =</span> <span class="cn">TRUE</span>))</span>
<span id="cb19-5"><a href="#cb19-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 87 × 4</span></span>
<span id="cb19-6"><a href="#cb19-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   name           homeworld  mass standard_mass</span></span>
<span id="cb19-7"><a href="#cb19-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;          &lt;chr&gt;     &lt;dbl&gt;         &lt;dbl&gt;</span></span>
<span id="cb19-8"><a href="#cb19-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Luke Skywalker Tatooine     77         -20.3</span></span>
<span id="cb19-9"><a href="#cb19-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 C-3PO          Tatooine     75         -22.3</span></span>
<span id="cb19-10"><a href="#cb19-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 R2-D2          Naboo        32         -65.3</span></span>
<span id="cb19-11"><a href="#cb19-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Darth Vader    Tatooine    136          38.7</span></span>
<span id="cb19-12"><a href="#cb19-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 83 more rows</span></span>
<span id="cb19-13"><a href="#cb19-13" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb19-14"><a href="#cb19-14" aria-hidden="true" tabindex="-1"></a><span class="co"># Subtract off homeworld mean</span></span>
<span id="cb19-15"><a href="#cb19-15" aria-hidden="true" tabindex="-1"></a>starwars <span class="sc">%&gt;%</span> </span>
<span id="cb19-16"><a href="#cb19-16" aria-hidden="true" tabindex="-1"></a>  <span class="fu">select</span>(name, homeworld, mass) <span class="sc">%&gt;%</span> </span>
<span id="cb19-17"><a href="#cb19-17" aria-hidden="true" tabindex="-1"></a>  <span class="fu">group_by</span>(homeworld) <span class="sc">%&gt;%</span> </span>
<span id="cb19-18"><a href="#cb19-18" aria-hidden="true" tabindex="-1"></a>  <span class="fu">mutate</span>(<span class="at">standard_mass =</span> mass <span class="sc">-</span> <span class="fu">mean</span>(mass, <span class="at">na.rm =</span> <span class="cn">TRUE</span>))</span>
<span id="cb19-19"><a href="#cb19-19" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 87 × 4</span></span>
<span id="cb19-20"><a href="#cb19-20" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # Groups:   homeworld [49]</span></span>
<span id="cb19-21"><a href="#cb19-21" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   name           homeworld  mass standard_mass</span></span>
<span id="cb19-22"><a href="#cb19-22" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;          &lt;chr&gt;     &lt;dbl&gt;         &lt;dbl&gt;</span></span>
<span id="cb19-23"><a href="#cb19-23" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Luke Skywalker Tatooine     77         -8.38</span></span>
<span id="cb19-24"><a href="#cb19-24" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 C-3PO          Tatooine     75        -10.4 </span></span>
<span id="cb19-25"><a href="#cb19-25" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 R2-D2          Naboo        32        -32.2 </span></span>
<span id="cb19-26"><a href="#cb19-26" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Darth Vader    Tatooine    136         50.6 </span></span>
<span id="cb19-27"><a href="#cb19-27" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 83 more rows</span></span></code></pre></div>
<p>Or with window functions like <code>min_rank()</code>:</p>
<div class="sourceCode" id="cb20"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb20-1"><a href="#cb20-1" aria-hidden="true" tabindex="-1"></a><span class="co"># Overall rank</span></span>
<span id="cb20-2"><a href="#cb20-2" aria-hidden="true" tabindex="-1"></a>starwars <span class="sc">%&gt;%</span> </span>
<span id="cb20-3"><a href="#cb20-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">select</span>(name, homeworld, height) <span class="sc">%&gt;%</span> </span>
<span id="cb20-4"><a href="#cb20-4" aria-hidden="true" tabindex="-1"></a>  <span class="fu">mutate</span>(<span class="at">rank =</span> <span class="fu">min_rank</span>(height))</span>
<span id="cb20-5"><a href="#cb20-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 87 × 4</span></span>
<span id="cb20-6"><a href="#cb20-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   name           homeworld height  rank</span></span>
<span id="cb20-7"><a href="#cb20-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;          &lt;chr&gt;      &lt;int&gt; &lt;int&gt;</span></span>
<span id="cb20-8"><a href="#cb20-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Luke Skywalker Tatooine     172    29</span></span>
<span id="cb20-9"><a href="#cb20-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 C-3PO          Tatooine     167    21</span></span>
<span id="cb20-10"><a href="#cb20-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 R2-D2          Naboo         96     5</span></span>
<span id="cb20-11"><a href="#cb20-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Darth Vader    Tatooine     202    72</span></span>
<span id="cb20-12"><a href="#cb20-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 83 more rows</span></span>
<span id="cb20-13"><a href="#cb20-13" aria-hidden="true" tabindex="-1"></a></span>
<span id="cb20-14"><a href="#cb20-14" aria-hidden="true" tabindex="-1"></a><span class="co"># Rank per homeworld</span></span>
<span id="cb20-15"><a href="#cb20-15" aria-hidden="true" tabindex="-1"></a>starwars <span class="sc">%&gt;%</span> </span>
<span id="cb20-16"><a href="#cb20-16" aria-hidden="true" tabindex="-1"></a>  <span class="fu">select</span>(name, homeworld, height) <span class="sc">%&gt;%</span> </span>
<span id="cb20-17"><a href="#cb20-17" aria-hidden="true" tabindex="-1"></a>  <span class="fu">group_by</span>(homeworld) <span class="sc">%&gt;%</span> </span>
<span id="cb20-18"><a href="#cb20-18" aria-hidden="true" tabindex="-1"></a>  <span class="fu">mutate</span>(<span class="at">rank =</span> <span class="fu">min_rank</span>(height))</span>
<span id="cb20-19"><a href="#cb20-19" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 87 × 4</span></span>
<span id="cb20-20"><a href="#cb20-20" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # Groups:   homeworld [49]</span></span>
<span id="cb20-21"><a href="#cb20-21" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   name           homeworld height  rank</span></span>
<span id="cb20-22"><a href="#cb20-22" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;          &lt;chr&gt;      &lt;int&gt; &lt;int&gt;</span></span>
<span id="cb20-23"><a href="#cb20-23" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Luke Skywalker Tatooine     172     5</span></span>
<span id="cb20-24"><a href="#cb20-24" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 C-3PO          Tatooine     167     4</span></span>
<span id="cb20-25"><a href="#cb20-25" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 R2-D2          Naboo         96     1</span></span>
<span id="cb20-26"><a href="#cb20-26" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Darth Vader    Tatooine     202    10</span></span>
<span id="cb20-27"><a href="#cb20-27" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 83 more rows</span></span></code></pre></div>
</div>
<div id="filter" class="section level3">
<h3><code>filter()</code></h3>
<p>A grouped <code>filter()</code> effectively does a
<code>mutate()</code> to generate a logical variable, and then only
keeps the rows where the variable is <code>TRUE</code>. This means that
grouped filters can be used with summary functions. For example, we can
find the tallest character of each species:</p>
<div class="sourceCode" id="cb21"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb21-1"><a href="#cb21-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span></span>
<span id="cb21-2"><a href="#cb21-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">select</span>(name, species, height) <span class="sc">%&gt;%</span> </span>
<span id="cb21-3"><a href="#cb21-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">filter</span>(height <span class="sc">==</span> <span class="fu">max</span>(height))</span>
<span id="cb21-4"><a href="#cb21-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 35 × 3</span></span>
<span id="cb21-5"><a href="#cb21-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # Groups:   species [35]</span></span>
<span id="cb21-6"><a href="#cb21-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   name                  species        height</span></span>
<span id="cb21-7"><a href="#cb21-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;                 &lt;chr&gt;           &lt;int&gt;</span></span>
<span id="cb21-8"><a href="#cb21-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Greedo                Rodian            173</span></span>
<span id="cb21-9"><a href="#cb21-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 Jabba Desilijic Tiure Hutt              175</span></span>
<span id="cb21-10"><a href="#cb21-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 Yoda                  Yoda&#39;s species     66</span></span>
<span id="cb21-11"><a href="#cb21-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Bossk                 Trandoshan        190</span></span>
<span id="cb21-12"><a href="#cb21-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 31 more rows</span></span></code></pre></div>
<p>You can also use <code>filter()</code> to remove entire groups. For
example, the following code eliminates all groups that only have a
single member:</p>
<div class="sourceCode" id="cb22"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb22-1"><a href="#cb22-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span></span>
<span id="cb22-2"><a href="#cb22-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">filter</span>(<span class="fu">n</span>() <span class="sc">!=</span> <span class="dv">1</span>) <span class="sc">%&gt;%</span> </span>
<span id="cb22-3"><a href="#cb22-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">tally</span>()</span>
<span id="cb22-4"><a href="#cb22-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 9 × 2</span></span>
<span id="cb22-5"><a href="#cb22-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   species      n</span></span>
<span id="cb22-6"><a href="#cb22-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;    &lt;int&gt;</span></span>
<span id="cb22-7"><a href="#cb22-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Droid        6</span></span>
<span id="cb22-8"><a href="#cb22-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 Gungan       3</span></span>
<span id="cb22-9"><a href="#cb22-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 Human       35</span></span>
<span id="cb22-10"><a href="#cb22-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Kaminoan     2</span></span>
<span id="cb22-11"><a href="#cb22-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 5 more rows</span></span></code></pre></div>
</div>
<div id="slice-and-friends" class="section level3">
<h3><code>slice()</code> and friends</h3>
<p><code>slice()</code> and friends (<code>slice_head()</code>,
<code>slice_tail()</code>, <code>slice_sample()</code>,
<code>slice_min()</code> and <code>slice_max()</code>) select rows
within a group. For example, we can select the first observation within
each species:</p>
<div class="sourceCode" id="cb23"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb23-1"><a href="#cb23-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span></span>
<span id="cb23-2"><a href="#cb23-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">relocate</span>(species) <span class="sc">%&gt;%</span> </span>
<span id="cb23-3"><a href="#cb23-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">slice</span>(<span class="dv">1</span>)</span>
<span id="cb23-4"><a href="#cb23-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 38 × 14</span></span>
<span id="cb23-5"><a href="#cb23-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # Groups:   species [38]</span></span>
<span id="cb23-6"><a href="#cb23-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   species  name    height  mass hair_color skin_color eye_color birth_year sex  </span></span>
<span id="cb23-7"><a href="#cb23-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;    &lt;chr&gt;    &lt;int&gt; &lt;dbl&gt; &lt;chr&gt;      &lt;chr&gt;      &lt;chr&gt;          &lt;dbl&gt; &lt;chr&gt;</span></span>
<span id="cb23-8"><a href="#cb23-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Aleena   Ratts …     79    15 none       grey, blue unknown           NA male </span></span>
<span id="cb23-9"><a href="#cb23-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 Besalisk Dexter…    198   102 none       brown      yellow            NA male </span></span>
<span id="cb23-10"><a href="#cb23-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 Cerean   Ki-Adi…    198    82 white      pale       yellow            92 male </span></span>
<span id="cb23-11"><a href="#cb23-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Chagrian Mas Am…    196    NA none       blue       blue              NA male </span></span>
<span id="cb23-12"><a href="#cb23-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 34 more rows</span></span>
<span id="cb23-13"><a href="#cb23-13" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 5 more variables: gender &lt;chr&gt;, homeworld &lt;chr&gt;, films &lt;list&gt;,</span></span>
<span id="cb23-14"><a href="#cb23-14" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; #   vehicles &lt;list&gt;, starships &lt;list&gt;</span></span></code></pre></div>
<p>Similarly, we can use <code>slice_min()</code> to select the smallest
<code>n</code> values of a variable:</p>
<div class="sourceCode" id="cb24"><pre class="sourceCode r"><code class="sourceCode r"><span id="cb24-1"><a href="#cb24-1" aria-hidden="true" tabindex="-1"></a>by_species <span class="sc">%&gt;%</span></span>
<span id="cb24-2"><a href="#cb24-2" aria-hidden="true" tabindex="-1"></a>  <span class="fu">filter</span>(<span class="sc">!</span><span class="fu">is.na</span>(height)) <span class="sc">%&gt;%</span> </span>
<span id="cb24-3"><a href="#cb24-3" aria-hidden="true" tabindex="-1"></a>  <span class="fu">slice_min</span>(height, <span class="at">n =</span> <span class="dv">2</span>)</span>
<span id="cb24-4"><a href="#cb24-4" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # A tibble: 48 × 14</span></span>
<span id="cb24-5"><a href="#cb24-5" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # Groups:   species [38]</span></span>
<span id="cb24-6"><a href="#cb24-6" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   name      height  mass hair_color skin_color eye_color birth_year sex   gender</span></span>
<span id="cb24-7"><a href="#cb24-7" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt;   &lt;chr&gt;      &lt;int&gt; &lt;dbl&gt; &lt;chr&gt;      &lt;chr&gt;      &lt;chr&gt;          &lt;dbl&gt; &lt;chr&gt; &lt;chr&gt; </span></span>
<span id="cb24-8"><a href="#cb24-8" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 1 Ratts Ty…     79    15 none       grey, blue unknown           NA male  mascu…</span></span>
<span id="cb24-9"><a href="#cb24-9" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 2 Dexter J…    198   102 none       brown      yellow            NA male  mascu…</span></span>
<span id="cb24-10"><a href="#cb24-10" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 3 Ki-Adi-M…    198    82 white      pale       yellow            92 male  mascu…</span></span>
<span id="cb24-11"><a href="#cb24-11" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; 4 Mas Amed…    196    NA none       blue       blue              NA male  mascu…</span></span>
<span id="cb24-12"><a href="#cb24-12" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 44 more rows</span></span>
<span id="cb24-13"><a href="#cb24-13" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; # ℹ 5 more variables: homeworld &lt;chr&gt;, species &lt;chr&gt;, films &lt;list&gt;,</span></span>
<span id="cb24-14"><a href="#cb24-14" aria-hidden="true" tabindex="-1"></a><span class="co">#&gt; #   vehicles &lt;list&gt;, starships &lt;list&gt;</span></span></code></pre></div>
</div>
</div>
<div class="footnotes footnotes-end-of-document">
<hr />
<ol>
<li id="fn1"><p>Note that the argument changed from
<code>add = TRUE</code> to <code>.add = TRUE</code> in dplyr 1.0.0.<a href="#fnref1" class="footnote-back">↩︎</a></p></li>
</ol>
</div>



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